A variety of different applications use sensor systems to detect the movement of an underlying object. For example, inertial sensors, e.g., accelerometers or gyroscopes, are typically used in safety and navigation systems for automotive, military, aerospace and marine applications. Sensors employing microelectromechanical systems (MEMS) devices are increasingly used in such applications due to their relatively small size and their capability to detect relatively small amounts or changes in the measured item.
MEMS devices typically employ a movable mass formed with one or more fixed, non-moving structures. For example, the movable mass may be suspended in a plane above a substrate and movable with respect to the substrate. The movable structure and the fixed structures form a capacitor having a capacitance that changes when the movable structure moves relative to the fixed structures in response to applied forces or acceleration, such as along a predetermined axis of the device, e.g., x-, y- and z-axes.
MEMS devices are often mounted or secured within packages because of the moving structures involved and the typical required device sensitivities. These packages may protect the device and permit electrical connections from the device to other components or systems. One type of package currently used for some MEMS devices is a premolded leadframe package. These types of packages typically include a preformed or premolded housing having walls surrounding a leadframe at the base of the walls to form a cavity. The electrical connections are then usually provided through the walls of the housing, and the device is coupled to the leadframe at the bottom of the cavity.
In some applications, the sensor die is parallel to the package mounting plane so that the device is in a horizontal orientation. In other applications, the sensor die is perpendicular to the board or base that the package is mounted on, so that the device is held in a vertical orientation. In this situation, the package may need to be robust enough in order for the MEMS sensors to be functional or to work properly. In some cases, however, the package may impart unacceptable levels of stress on the device or may impart unacceptable levels of vibration to the device making it unusable.